Surface Condensers: Design and Efficiency

Surface Condensers (Non-Mixing Type Condensers)

• Use indirect heat transfer, preventing contamination and allowing condensate reuse.
• Efficient tube arrangement leads to steam condensation for various applications, despite initial cost challenges.

Requirements of a Good Surface Condenser

• Steam should enter the condenser with least possible resistance for easy flow.
• Steam should be well distributed in the vessel with minimum pressure drop.
• Circulating cooling water should flow through tubes with least friction.
• Rise in temperature of cooling water should be limited to 10°C for better thermal efficiency.
• No undercooling of the condensate, steam should lose only its latent heat to the circulating water.
• Tubes should be made of high thermal conductivity material.
• No leakage of air from the condenser.

Jet Condensers (Mixing Type Condensers)

• Direct contact between exhaust steam and cooling water.
• Temperature of the condensate matches the cooling water leaving the condenser.
• Heat transfer occurs through direct conduction between steam and water.
• Cooling water impurities limit condensate reuse, causing loss and higher pump power.

Types of Jet Condensers

• Low-level jet condensers: parallel flow type and counter flow type.
• High-level jet condensers: use gravity to direct condensate and cooling water into the hot well.

Steam Condenser

• Device in which exhaust steam from the steam turbine is condensed by means of cooling waters.
• Condensation done by removing heat from the exhaust steam using circulating water.

Advantages of a Condenser in a Steam Power Plant

• Increases efficiency of the power plant due to increased enthalpy.
• Reduces back pressure of the steam, resulting in more work output.
• Reduces temperature of the exhaust steam, resulting in more work output.
• Condensed steam can be reused as feed water for boiler, reducing cost of power generation.
• Temperature of the condensate is higher than that of fresh water, reducing heat supplied per Kg of steam produced.

Other Important Functions of Condensers

• Create a vacuum by condensing steam.
• Remove dissolved non-condensable gases from the condensate.
• Provide a leak-tight barrier between the high-grade condensate and the untreated cooling water.
• Provide leak-tight barrier against air ingress, preventing excess back pressure on the turbine.

Elements of a Steam Condensing Plant

• Condenser
• Condensate extraction pump
• Air extraction pump
• Hot well
• Boiler feed pump
• Condenser cooling water pump
• Make-up water pump
• Cooling tower or spray pond
• Relief valve